The invention relates to an apparatus for comminuting waste of synthetic plastic material, comprising a housing in which at least one rotor is bearingly supported for rotation by a motor around a preferably horizontal axis, which rotor on its periphery is provided with comminuting tools, in particular knives, acting onto the supplied material. Counter tools, in particular counter knives, are stationarily disposed within the housing, which forms a supply shaft of great volume. The counter tools are assigned to the comminuting tools. The apparatus also has supply means with a slide member pressing the material disposed within the supply shaft against the rotor.
Comminuting apparatus are known in a plurality of embodiments as shown, for example, by EP 605 382 B1, AT 398 712 B. Investigations by the applicants have shown that the comminuting effect or, respectively, the throughput is highly dependent on the position of the slide member relative to the rotor. As soon as the slide member at its forward motion reaches a position relatively close to the rotor, the comminuting effect is increased and remains at a high level until the entire material dammed up between the rotor and the slide member is worked up. When the slide member is retracted in order to bring fresh material to be comminuted into the area between the rotor and the slide member, the comminuting efficiency of the apparatus decreases considerably. When the slide is again moved towards the rotor, the comminuting efficiency remains at a low level, as long as the distance between the rotor and the slide is still great. A high throughput of the apparatus is only obtained when the slide has reached a comparatively low distance from the rotor. An explanation for this is that the slide member in its position adjacent the rotor forms an intake gap for the material to be comminuted, which gap acts in the manner of a guide blade.
The described pulsating or varying throughput behavior is already of disadvantage within a mere comminuting machine, because the average throughput per time unit is low when compared with the maximum value. In particular of disadvantage are the circumstances, however, within a plant for comminuting synthetic plastic material, in which an extruder immediately follows the comminuting apparatus, because due to the uneven throughput of the comminuting machine, the extruder efficiency also varies considerably, so that the final products obtained at the extruder exit, for example within a forming plant, become highly uneven.